The present invention relates to a cutting tool, such as, for example, a rotatable cutting tool which is a component of an earth-working apparatus, used to impinge upon earth strata such as, for example, ore-bearing or coal-bearing earth (or mineral) formations, as well as asphaltic roadway material. More specifically, the present invention pertains to such a cutting tool that includes a cutting tool body that contains a hard cutting tip at the axial forward end thereof. The cutting tool body, and especially the portion of the cutting tool body adjacent the axial forward socket that receives the hard cutting tip, has improved strength properties, as well as improved retention of the hard cutting tip to the cutting tool body.
Heretofore, a rotatable cutting tool has been used to impinge upon earth strata, such as for example, ore-bearing or coal-bearing earth (or mineral) formations, as well as asphaltic roadway material and the like. Such a rotatable cutting tool typically comprises an elongate cutting tool body that has an axial forward end and an axial rearward end. In one embodiment of such a cutting tool, the cutting tool body has a socket at the axial forward end wherein the socket receives a hard cutting tip. In such an embodiment, the hard cutting tip is affixed to the cutting tool body by brazing or the like.
As can be appreciated, during operation the entire rotatable cutting tool is typically subjected to a variety of extreme cutting forces in an abrasive and erosive environment. It would be undesirable for the cutting tool body to prematurely wear or fail (whether it be through catastrophic fracture or the like or through abrasive or erosive wear) prior to the hard cutting tip wearing to the end point of its useful life. Further, would be undesirable for the hard cutting tip to become detached prematurely from the cutting tool body, whether it be through catastrophic fracture or the like, prior to the hard cutting tip or the cutting tool body wearing to the end point of their useful life.
In either circumstance, the rotatable cutting tool would have to replaced prior to the normally scheduled time for replacement. Further, the premature failure of the rotatable cutting tool would negatively impact the cutting or milling efficiency of the overall earthworking (e.g., mining) apparatus. It thus becomes apparent that it is important that the cutting tool body possess the requisite strength to maintain its integrity during the intended useful life of the rotatable cutting tool. It is also apparent that it is important for the hard cutting tip to remain attached to the cutting tool body throughout the intended useful life of the rotatable cutting tool.
Heretofore, a cold-heading or cold-forming process has been used to form some portions of the cutting tool body. One exemplary patent is U.S. Pat. No. 4,627,665 to Ewing et al. that shows the cold forming of a cutting tool body. However, a number of steps are necessary to form certain portion of the cutting tool body. For example, the puller groove is formed via a separate roll-forming operation while the socket and the axial forward portion of the rotatable cutting tool is formed via a cold-heading process. U.S. Pat. No. 6,397,652 to Sollami is another example of a patent that shows a cutting tool body formed by a cold forming process.
U.S. Pat. No. 7,360,845 B2 to Ojanen is still another example of a cutting tool body formed by a cold forming process. This patent shows a cold-headed puller groove and a cold-headed socket. However, the cold-headed socket of this patent is a shallow socket. In the specific embodiment, the shallow socket has a depth equal to about one-seventh of the diameter of the shallow socket.
It can therefore be appreciated that it would be desirable to provide an improved cutting tool body, including a rotatable cutting tool body, that exhibits improved strength properties. It can also be appreciated that it would be desirable to provide an improved cutting tool body, including a rotatable cutting tool body, that minimizes the tendency to prematurely wear or fail (whether it be through catastrophic fracture or the like or through abrasive or erosive wear) prior to the hard cutting tip wearing to the end point of its useful life. Further, it would be desirable to provide an improved cutting tool, including a rotatable cutting tool, that minimizes the tendency of the hard cutting tip to become detached prematurely from the cutting tool body, whether it be through catastrophic fracture or the like, prior to the hard cutting tip or the cutting tool body wearing to the end point of their useful life.